1. Field of the Invention
This invention relates generally to analysis of chemical compounds by a gas chromatograph (GC). In particular, this invention relates to the analysis of certain organochlorinated chemical compounds by a gas chromatograph with a three dimensional quadrupole ion trap mass spectrometer as its detector.
2. Background
For many years it has been common place to analyze chemical compounds through the use of a mass spectrometer. More recently, quadrupole ion trap mass spectrometers have been used. In a ion trap such as that disclosed in U.S. Pat. No. 5,055,678 a heated sample is injected into a cavity defined by a plurality of electrodes. The sample is ionized and then analyzed in the ion trap.
It is clearly critical that the electrodes not react with the sample being analyzed in the ion trap. Once a reaction takes place, it will corrupt the sample and therefore the analysis will be less than credible.
In the analysis of typical chemical compounds the electrodes of an ion trap do not react to any noticeable extend with the sample. However, certain organochlorinated compounds used in pesticides have the effect of causing a reaction with electrodes now in use. As will be demonstrated below, with reference to FIGS. 2-18, this reaction has the effect of certain tailings which corrupt the ionized sample and do not allow proper analysis.
Organochlorinated compounds such as Lindane, Methoxychlor and Parathion are among the most hazardous chemicals known to mankind. Even in small amounts such chemicals are extremely hazardous and fatal to human beings and other living creatures. Even moderate concentrations or the fear of the same has closed highways, shut down industries, killed rivers and streams. It is therefore critical that such chemicals be easily and reliably detected. Unfortunately, until recently and for many years prior, there have been difficulties in detecting and analyzing such chemicals because of their corrosive and destructive nature.
Typical electrodes now used in an ion trap are made from stainless steel. While testing typical compounds, the stainless steel electrodes have proven serviceable. However, when used with the organochlorinated compounds noted herein, the electrodes do have a markedly tendency to chemically react.
Improvements in the electrodes have been attempted. For example, in the above noted U.S. Patent, the stainless steel electrodes were coated with chromium or oxidized chromium surface. However, even using such electrodes, it has been found that the sample containing organochlorinated compounds have been degraded and the analysis corrupted.
What is needed is an ion trap that does not chemically degrade the organochlorinated compounds commonly found in pesticides. Additionally, what is needed is an ion trap which does not produce chromatic tailing with the same samples.